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How does a wedge gate valve work?
A wedge gate valve is a type of multi-turn valve that uses a rising or non-rising stem. The stem rotates several times to either start or stop the valve. The valve begins by rotating the handwheel in a clockwise direction. Turning the handwheel makes the stem rotate as it moves upwards. The upward movement of the stem also makes the valve disc move upwards. As such, the valve is made open, allowing fluid to flow through the valve. Fluid flow keeps going on unless the valve is closed. The valve is closed by rotating the handwheel in the anticlockwise direction. As such, the stem rotates as it moves downwards. The downward linear movement of the stem forces the valve disc to return to its seating position. As such, the valve’s central hole where the fluid flows through gets blocked, which stops the valve. The valve then gets closed, and no fluid flows.
Figure: Working of a wedge gate valve.
Applications of wedge gate valve
Advantages of wedge gate valves
Disadvantages of wedge gate valves
Troubleshooting wedge gate valves
The valve needs high operating torque to open/close.
The valve does not close/open completely.
Leakage through the stem packing
Leakage through the gasket
Leakage through the valve body/bonnet
Summary
Wedge gate valves are valves that operate by using a wedge disc to start or stop fluid flow. The valve uses a wedge-shaped gate (disc) to enhance the high seating area to ensure the valve can seal perfectly to the body. This type of valve operates using a manual handwheel or actuators like electric or pneumatic. Whether the valve is operated manually or using actuators, the working principle is to turn the valve stem so that the valve disc can move upwards or downwards. When the stem rotates to move up, it forces the disc to open the valve for fluid flow. On the other hand, when the stem turns to move downwards, it causes the disc to move downwards, where it finally closes any fluid flow. The choice of temperature level depends on the valve seat material. Seats made from metallic materials are ideal for temperatures above 65o C, while rubber or plastic are used below 65oC. Wedge gate valves are suitable for use in high and low temperatures.
Wedge gate valve manufacturers produce varieties of these valves, among them rising stem valves, non-rising stem valves, electrically actuated valves, and pneumatically actuated valves. Applications of these valves include chemical industries, water supply, power plants, mining, foods and beverages, paper, and pulp, among others. The advantages of this type of valve are that it is easy to clean and repair, versatile in size, has bi-directional fluid flow, low-pressure loss, and high strength.